1. Field of the Invention
The present invention relates to a tilt adjusting apparatus employed in a disk drive which performs recording and/or playing back of optical disks. More particularly, the present invention relates to a tilt adjusting apparatus which performs an accurate adjustment in a relation between an optical axis for reading signals and a surface on which signals are recorded.
2. Description of the Related Art
Recently, disk drives which utilize optical disks such as CDs, magnetic optical disks, DVDs, etc., as information recording mediums has become increasingly popular. A typical disk drive of this type comprises: an optical pickup for reading signals by irradiating an optical disk with an optical beam; a feeding mechanism for translating the optical pickup in a radial direction of the optical disk; a turntable which carries the optical disk; a spindle motor for revolving the disk on the turntable; a loading mechanism for inserting/ejecting the optical disk; and other components including circuit elements. With such a disk drive, an angle between the optical axis of the beam radiated from the optical pickup and the signal-recorded surface of the disk must always be constant for the signals to be read accurately. The disk surface, however, tends to tilt relative to the optical axis due to the following factors. That is, mechanical factors such as a tilt in the feeding mechanism, swaying of the surface of turntable, and differences between component products, or other factors such as warp of the disk.
To compensate for this, disk drives are generally provided with tilt adjusting apparatuses to adjust the tilt of the disk surface. An exemplification of tilt adjusting apparatuses will be described below. Referring to FIG. 6, a shaft 2a of a spindle motor 2 is fixed to a turntable 1 at the center. An angle xcex82 between the axis of the shaft 2a and the turntable 1 is kept right by a supporter 3.
The shaft 2a and the supporter 3 are inserted through a hole 9a formed in chassis 9 without contacting the chassis 9. On the upper side of the of the spindle motor 2, which is the side closer to the chassis 9, a mounting plate 5 is attached. Tapped holes 9b and 9c are formed in the chassis 9, while small holes 5b and 5c are formed in the mounting plate 5 at positions corresponding to the tapped holes 9b and 9c, respectively.
A fastening screw 6b is inserted through a small hole 5b and through a coil spring 8b which is sandwiched between the chassis 9 and the mounting plate 5, and is screwed into the tapped hole 9b. Meanwhile, another fastening screw 6c is inserted through a small hole 5c and through a spacer 7 which is also sandwiched between the chassis 9 and the mounting plate 5, and is screwed into the tapped hole 9c. 
The operation of the above-described tilt adjusting apparatus of conventional type will be described below. By rotating the fastening screw 6b to change a depth of insertion, it is possible to cause the mounting plate 5 to swing about a fulcrum 7a on the spacer 7. This provides the tilt adjustment of the spindle motor 2 which is fixed to the mounting plate 5, and thus realizes a tilt adjustment of the disk placed on the turntable 1.
As for the tilt adjusting apparatuses of conventional type having above-described construction, the center upon which the mounting plate 5 swings to adjust a tilt is the fulcrum 7a of the spacer 7. When the tilt adjustment is performed, therefore, vertical position of the center of the turntable 1 varies. In addition, the rotational center of the turntable 1 shifts in a horizontal direction; thus, when the optical pickup utilizes, for example, three spots of one main beam and two subbeams for tracking, a difference of phases may be caused in signals of subbeams, which results in inferior play-back ability.
The present invention aims to solve the above-described problems encountered by conventional tilt adjusting apparatuses.
Accordingly, it is an object of the present invention to provide a tilt adjusting apparatus, which has a simple construction, and which is capable of making an accurate adjustment without causing a displacement of the center of the disk.
A tilt adjusting apparatus according to the present invention is applicable for a disk drive having a turntable for carrying a disk, a spindle motor for revolving the turntable, an optical pickup for reading signals recorded on the disk, and a drive plate for supporting the optical pickup. To achieve the above-described object of the present invention, a tilt adjusting apparatus according to the present invention comprises: a skew plate which is fixed to or combined with the spindle motor; a supporter unit for supporting the skew plate over the drive plate in such a manner that the skew plate is tiltable around the central point of the signal-recorded area of the disk; a first adjuster unit which has an adjuster screw for applying force to the skew plate in a first direction which is perpendicular to a tracking direction of the optical pickup, and which thereby tilts the skew plate so as to adjust a tilt of the disk on the turntable in the first direction; and restraining means for restraining the skew plate from moving in a second direction, which is a direction parallel to the tracking direction of the optical pickup.
In the above-described tilt adjusting apparatus, the adjuster screw is used for applying force to the skew plate in the first direction which is perpendicular to a tracking direction of the optical pickup. This results in a tilting of the turntable which is attached to the spindle motor in the first direction around the central point of the signal-recorded area of the disk. Accordingly, the tilt adjustment of the disk in the first direction is realized, without causing a displacement of the disk in the vertical direction. During this operation, the restraining structure restrains the skew plate from moving in the second direction which is parallel to the tracking direction of the optical pickup. The center of the disk, therefore, does not shift in the second direction when the adjuster screw applies force to the skew plate.
The supporter unit may have at least one gradient portion which slidably supports the skew plate at the bottom. The gradient portion supports the skew plate, while the skew plate slides thereon; therefore, the tilt adjustment is achievable without changing the vertical position of the center of the disk which is mounted on the turntable.
The supporter unit may also have at lease one elastic supporting member for supporting at least one of two opposing points in the skew plate, and the tilt adjusting apparatus may also have a second adjuster unit for adjusting a tilt of the disk in the second direction by applying force to the skew plate in a direction parallel to the axis of revolution of the disk.
The second adjuster described above is used for applying force to the skew plate, so that the elastic supporting member stretches or shrinks. Accordingly, the turntable which is attached to the spindle motor tilts in the second direction which is parallel to the tracking direction of the optical pickup around the central point of the signal-recorded area of the disk. This realizes the tilt adjustment of the disk in the second direction without causing a displacement of the disk in the vertical direction.
As described above, the present invention provides a tilt adjusting apparatus for a disk drive, which has a simple construction, and which realizes an accurate adjustment without causing a displacement of the center of the disk.